Apparatus for the manufacture of bifocal lenses.



M. BENTZON & A. H. EMERSON APPARATUS FOR THE MANUFACTURE OF BIFOUALLENSES APPLICATION FILED NOV. 18, 1909.

Patented Jan. 13, 1914.

3 S-HEE T S-SHEET l.

.M. BENTZON & A. H. EMERSON. APPARATUS FORYTHE MANUPAGTURE OF BIPOOAL LENSES. APPLICATION FILED NOV. 18, 1909.

11 8 5293 ,li,. Patented*'-Jan.13,1914.'

s SHEETS-SHEET 2.

M. BENTZON @zA. H. EMERSON. APPARATUS FOR THE MANUFACTURE OF BIFOOAL'LENSES. APPLICATION FILED 110v.1s, 1909 1,084,529. Pawnted Jan. 13, 1914 3 SHEETS-SHEETS.

f insasze.

I residing at 188 'Strand, and

\ jects of the King of December 1905 Serial tool spindle 'To all whom it may concern I ing drawings.

" STATES PATENT *onnicn.

moons nnn'r'zon Ann .snrnnn 11mm! Bunsen,

or Lennon, mmmnn.

.AI'PABATF'S FOR THE MANUFACTURE OF BIFOCAL'I ENiES.

' Specification of Letters Patent.

.PaterltedJan. 13, 1914.

Original application fledmecember 18, 1905, Serial No. 292,398. Divided and this afi'piieation fled November MALCOLM Bnnrzon', ALrunn HENRY Eminson, residing atN26 Eyre Street Hill, Clerkenwell, both of London, England, sub- Great Britain, have in- Be it known that'we,

Qvented new and useful Improvements in Aparatus for the -Manufacture of Bifocal uses, of which the following is a specification, reference being had to the accompany This invention relates to apparatus for the manufacture of bi-focal lenses by the improved process forming the subject of our applicaton for a. patent filed on-the 18th No. 292,393, of which; this application is a division.

Figure 1 shows in elevation and section the ordinary form of bi-focal lens. Fi 2 is a section illustratingthe new :form 0 bifocal lens made by the im roved apparatus. Fig. 3 is a sectional side e evat-ion of a ma chine constructed according to this invention for grinding bi-focal lenses. Fig. 4 is'a plan illustrating-the simultaneous operation of two of" he saidmachines. Fig, 5 is a plan illustrating a modified arrangement of the operating tools. Figs. 6 and 7 are in: spectively asectional elevation and a illustrating a form ofglass disk from w ich the lenses may be produced. I Eig. 8 is a ver- V tical section illustrating a machine provided with twotoo'l spindles for the simultaneous grinding of two surfaces. Figs. 9 and 10 are respectively a vertical section and an underside View of one form of grinding tool to be used in carrying out the invention. Figs. 11 and .12 are respectively a sectional elevation and a plan of the lower part of another form, ofgrinding tool. Figs. 13 and ll are respectively a sectional elevation and an underside view of a holder for two lenses, while being ground. Figs. 15 und. 16 are respectively a sectionalelevation and 3 Ian illustrating a modified form of lens ho der.

Referring to Fig. 3, 1 is the frame carry ing a bed 2, capable of adjustment n a vertical direction, and of fixation, and in this rotates the spindle 3 on 'whichis fixed adisk 3", for carrying the lensholder --The 4 is carried inn carrierhead 5 on an arm (5, and this has aweight (Sf, by

which the pressure on the work can be regus 7 lated. The

arin 6 is pivoted at the endto a spindle 4 to be placed 'other hand to take u lan v to diminish that ofa concave 18, 1909. Serial H0. 528,800.

lever 7 The lever 7 is in one piece with the block 7",-and the whole rests upon a spring 23, and can be adjusted by a screw 8, so that the other end of the arrn6 with the carrier head 5 can be moved in any required direction, so as to allow the tool 9 carried by the over the glass or glasses 10. The arm 6 is held up by a support 8" when it isturned back. The grinding tool is at a distance from its axis of rotation. In the present instance the grinding tool is provided with an annular grinding surface as shown. The tool 9 is so' attached to the spindle as to be on the one hand easily secured to or removed from it, and on the automatically the proper position upon t e glass,-and to re;- tain it while the latter is being ground. In the example shown, this is attained by a joint consistin of a ball-point 11 on the end of the spin 1e 4, which enters a corresponding hollow in the axis of the tool. A tongue 12 lies in slots in the collar 13 on the spindle 4, and at the upper part of the tool 9, and thus transmits the motion of the spindle to the tool,-

The spindles 3 and 4 are provided with pulleys, which allow of the alteration of the proportional velocities, so that by controlling the relative velocities of grinding between the work and the tool, any desired curvature can be obtained, 1

constructed so thatits grinding surface is located wholly so in any desired position In Fig. 3 the tool is so set that the middle line of-the actin surface passes through, on the periphery o the tool, the axis of rotationof .the spindle 3, and sothrou'gh the ometrical center of the surface which is eing worked. If creasethe curvature of a convex surface, or one, the lower spindle mustrotate rapidly, while the tool revolves slowly,'- and, most suitably, inthe opposite direction. f If, forinstanceythe work be setrotatin at 400 revolutions per minute in one" direction, and the tool executes 100 in the contrary direction, there will evidently be more friction at the'periphery of the surface of the work than at its center. The edge will consequently be ground down faster than the center, and a convex surface now itbe .desired to inwill become more convex, while a concave V .one'will become less concave, -and, indeed,

' the tools have 400 revolutions and the work 100 per minute, it is clear that the resultant velocity of grinding at the edge of the surface operated upon will come out very small,

- while in the center the tool will move rapidly over the surface, and will in consequence grind the glass away quickly at this point.

The exact curvature can be determined by spherometers. Assoon as the desired curve is obtained, the tool for rough grinding is substituted by the tools for smoothing and polishing, and the glass is smoothed and polis hd Without further alteration of. the curve. The proportion of velocity which must be arranged so that no chan e in the curve shall occur, will soon be foun by trial. A In Fig. 3 of the drawing for example the spindle 4: of the grinding tool is shown provided with two grooved pulleys,of different diameters for engaging a driving belt from a driving shaft which may be operated in any desired way, and the spindle 3 of the work holder-is shown provided withffour grooved pulleys for engaging a driving belt from a suitable driving shaft.- When it is desired to drive the spindles or either of them in the opposite direction the driving may conveniently be accomplished by means of thejsam'e belts, by simply reversing the direction of rotation of the said driving shaft or shafts" in any usual manner.- We

driven at 'tlon.

have not deemed it necessary herein to.ex-. tend the illustration of the invention'beyond the driving belts above mentioned, by which the said spindles or either of them may be varying speed and in either direc- In Fig. 3 the grinding machine shown in action as. arrangedfor grinding asecond curve .on a lens already possessing one curve 2'. e. on a finished spectaclelens, and there; are attached to the lower spindle, by an arrangement to be described later, two lenses 10, for exact centering of the two sections of .the lens, these meeting in. the axis of rotation of the work spindle, so that both lenses can be ground and provided 'asecond' curvature at the same time.

If two curves are, to. be ground at one operation, two machines of the kind shown in Fig. 3 can be used, their tools 9 being applied to the surface' mder treatment in the manner shown in F g. 4 The' tool of the one'machine .1s so set that its periphery passes. through the axis of rotation of the revolving-work,"and touches 'the line of separatio'n between the twopcurves, while the other tool is setbetween the line of separation and; the: periphery of the surface of the work. Instead of twomachines there may be used a single one having on the frame 1 two arms with two-tool spindles 4.

Instead of allowing the work carrier to r0- tate, it maybe fixed, and the tool alone allowed to rotate, in which .case the tool or tools rotate upon their spindles, and at the same time execute a motion in a circle around the center-cf the surface being worked, as shown in outline in Fig. 5.

The two curves maybe worked upon a single flat disk, which is cut into several pieces, from which by grinding the under surfaces, the complete lenses are produced. Such a glass disk, with the two curves on the upper surfaceisfishown with its holder in Fig. 6. Instead of this however, as shown in Fig. 7, the two glasses or lenses mightbe cut first so as to meet along a straight line,

the spaces between them being filled up by fish-tail pieces 25%, so that a coherent surface for grinding is obtained. In some cases it is advisable to use an ordinary tool before only the tools revolve, .is shown in Fig; 8.

The inner tool is carried by a spindle 25 in bearings on-an arm 26 which is attached to the sleeve 27. The s indle is. driven b means of the toothed w eels 28, 29 of whic the latter is fixed to the axle 30, and is driven by a belt passing around the pulley 31. The sleeve 27 is provided with driving pulleys 32. The outer tool is carried by the spindle 33', which has its bearin 34 on an arm 35. The arm 35 is removab y attached to the sleeve 36 which is borne by the head carries a toothed wheel 0, which engages with a toothed wheel 41 on the spindle 33.

I n this way each has imparted to it a rotatron upon its own axis and a planetary 'motion. The arm 35 which carries the bearing 34- for'the outer'tool may, according to the size of the shorterarms.

In the drawing only one tool is shown at work upon the outer surface. Two' or. more tools'may, however, be. made use of, while a single tool may be appropriately the inner 'surface. (See Fig. 5.)

glass, be replaced by longer or 1'20 used for In producing bi-focal lenses by grinding" a secondcurve on a lens already having a single curve (a finished spectacle lens). any desired position of ,the'o-ptical center of the lens may be attained by the following arrangement. The lens holders are'sccured to a block 16 of metal or other suitable matcrial, Figs. 3, 13, 15, which is carried by a for grinding concave lenses, in which the chuck or work spindle. This block is best made of sucha size that it will carry two responding to the curve of the lenses to be. ground, the curves to be ground, '5. e. superadded and the desired position of the optical legs run outward the lens .to be removed. Before center. By a'calculation'familiar to experts the correctangles' for lenses of all curvature's can be readily determined.

'According to Fig. 3, which shows an a paratus for grinding two convex lenses, t e legs of the angle run outward and down-. ward, while Figs. 13 and 14 show a block and upward. Fig. 13 is a vertical section, and Fig. 14 a view from beneath.

The block 16 has an aperture each of the two inclined faces, in which the stem of a lensholder 17 is secured by means of screws. 19 The position of the holes'naturallyv depends upon the magnitude of. the angle under which the surfaces which carry holders are inclined to each other. The block 16 is secured to the chuck 3*" at the top of the spindle 3 by screw bolts, which are screwed down by nuts 20, so thatthe heads of the 'screw'bolts rest against the undercut part of the slots 21, which, when the nuts 20 are slackened, allow the block 16.

the lenses (after being cemented to the lens holders) are secured to the block 16, they niust be exactly centered upon the lens holders. A portion of each lens is cut away, so that both lenses can be brought under a single grinding or polish-' ing tool and operated upon by it, as is shown in Fig. 3'. The block 16 may have three or more surfaces instead of two, these being inclined to the axis of rotation of the work under the same angle, and having each an aperture for the reception of a iens holder.

'In this case three or more lenses can be worked simultaneously, and these again are to base cut, that the portions of the lenses upon which. the tool is to operate abut upon each other. r

If the block 16 be employed for grindinga lens, in which the 'part of it intended or reading exceeds a radius and the glass consequently projects over the lens holder, only one lens holder can be. fixed to the block 16. Instead of the block 16 having flat bearing surfaces, it may consist of a curved headpiece, as shown in Fig. 15 inxertical section,

and in plan in outline in Fig. 16. The lower sides of the lens holder 17 are then so cutout as to fit the curve of the block 16, and the -cal -ulati0ns are made for tangents to the curved surfaces at the central point of the lens holder.

In bi-focal lenses with a prominent dividing line, or a-ridge betweenlthe two portions stance, by hol ridge grinding of the two curves the ridge dioxins a third reflecting surface, which is very irritatin and injurious to the eye of the wearer,

(Fig. 1) such as are obtained by fi? and since the ed e of the ridge is sharp, the

lens is very easi y' injured, if it comes into contact with a hard surface. The fault can be overcome by darkening or graying the ridge or leaving it unpolished, so that it offers no reflecting surface, fering the sharp'edge Oil, the ridge, so that the lens cannot be "injured if it comes into contact with a hard surface. This may be efiected' in any convenient way, as'for inin a copper strip against the while the lock 16 carrying'the lens holder rotates. In casesin which the lenses have to be decentered, the lens holder can be tilted by laying packing disks under it to the desired amount.

Various terms of constructing the tools areshown in Figs. 9, 10, 11 and 12. Figs. 9 and 10 show in vertical section and from below the .under part of a hollow tool in which the hollow instead of being merely annular is specially shaped so that the part of the grinding surface which grinds most heavily is the strongest, it being at the same time supposed that the tool is to be used for grinding convex lenses, in which case'the glass is ground more strongly toward the edge than in the center. The grinding either. flat or curved.

1 Figs. 11 and l2 show in vertical section and in plan another form of hollow tool. Fig; 11 specially shows the method of attac ing the tool to the spindle. In the inside of the 'tool'isa spring 14, so arranged that it holdsthe ball-point 11 at the end of the spindle in the recess of the tool, so that the tool can be removed from or attached to the spindle by pushing on one side the spring of and by chamsurface may be the bar 11. The tool is one for polishing,

and carries polishing material 15 Jon the working edge.

10 is moresuitable .for the two latter proe cases than 'for the former.

.The'pgol' -felt or corresponding material-l inu'st e made suificiently hard, so that the surfaces produced upon the lenses may be perfectly polished spherical ones. For this pur ose the felt or other material may be boile in pitch. Rou e or anysother suitable material may be use for po hing.

The tools for smoothing may suitably be no Instead of attaching the tools to the spin- 'dle insthe way described, they may be 50- made of a rather softer metal such as brass, than those for roughing, which may for example be made of steel,

In the following claims we'have used the expression relative rotary movement of the tool and work holder to define the relations of these parts as the .tool may be held stationary with its axis at one side of the axis .of the work holder, which is revolved on its axis as in Fig. 3,'or the tool may be given a bodily rotation around a point on the work holder as in Fig. 8.- We have also referred in said claims to the fact that the tool is supported with its axis at a distance from the center of this relative rotary movement,-

the. axis-of said relative rotary movement being obviously the axis of the work holder, where that revolves and bein the axis about which the tool revolves bo ily', Where the tool-is revolved with respect to the work holder. c

It will be obvious that by lacin the annular universally supporte too herein :shown and described in engagement with. any 'spherical'surface of greater diameter than the tool, whether such surface be convex orffionca-ve, annular portions of the tool and in what manner the same is to be performed, we declare thatwhat we claim is -1. In a grinding apparatus for producing spherical surfaces, the combination of a rotatable grinding tool, having its entire grinding surface located at a distance from its axis of rotation, a workholder, means for causing a relative circularmovement between the axis of the tool and the workholder, means for supporting said tool with its axis at a fixed distance from the center of the circle of said relative movement, said tool being movable toward the workholder and beingfree at all times to follow with its abrading surface, the surface, of the work which it engages, whereby the speed and direction of rotation of the tool"an d'- the speed and direction of said circular relat1ve,move-" ment Wlll determine the character of the spherical surface produced-by said tool.

2. In a grinding apparatus for producing spherical surfaces, the combination -of-a rotary grinding tool having its grinding surface located at a distance from its axis of rotation, whereby 'said tool abrades in an annular path, a work-holder, means for causfing arelative circular -movemen.t between the axis of thetool and the workholder,

means for supporting the-said tool with its distance from the center of said relative movement, said the circle OI tool being movable toward the workholder free .at all times to follow Wltll and being its abrading surface the surface of the work which -it enga es, and means for driving 'saidtool at di erent speeds. l

3. In a grinding apparatus for producing spherical surfaces, the combination of a rotatable annular grinding tool having its grinding surface located ata distance from its'axis of rotation, a workholder, means for supporting said tool with its axis at one side of the center of, the workholder, and with annular portions of-its inding surface in operative relation with t e surface operated upon, means for establishing a relativecircular movement between the workholder and the axis of said tool, concentric with the center of th'e workholder and means for driving said to'o1'.-

4. In a grinding apparatus for producing spherical surfaces, the. combination of a-r0;-,.

tatable grinding tool having its grinding surface located at a distance from its axis of rotation, a rotatable workholder,.means for supporting said tool with itsaxis between the axis of rotation of the workhplder and the peripheral portions thereof, said tool being movabletoward the workholder and being free to follow with its abrading surface the surface of the work.

"5. In a grinding apparatus for producing spherical surfaces, the combination of a rotatable grinding tool having an annular grinding surface, a rotatable workholder,

means for supporting said tool withits axis between the -.?axis of rotation of the workholder and the periphery thereof, said tool being at all times free to follow with its abrading surface the surface of the work, means for driving said tool and means for rotating said Workholder. V

6; In a grinding apparatus for producing spherical surfaces, the combination of arotatable workholder of a grinding toolhaving an annular grindingsurface', a driving spindlejfor said tool connected thereto by' means permitting the grinding surface of the tool to followthe surface of. the work and means for support ing saidspindle with its aims at a distance from the :axis of rotation ofthe workhol'der, 'means for driving said workholder at different speeds and means for driving said tool spindle at different speeds.

7. In a grinding apparatus for producmg spherical surfaces, the combination with a horizontal-rotatable work holder, of a vertically disposed driving spindle, a carrier head provided with bearings for'said spindle, a support for said carrier head connected theretoby a horizontally disposed pivot,

I and an annular grinding tool having a universal connection with the said spindle, said support and carrier head holding the spindleat all times in a position at one side; of the axis of rotation of said work holder. 8. In a grinding apparatus for producing spherical surfaces, the combination Wlilhia horizontalrotatable work holder, of a verihorispntalrotatable work holder, of a vertically, disposed driving spindle, a carrier head provided with bearings for said spindle, a support for said carrier head connected thereto by a horizontally'disposed pivot,

and an annulargrinding tool havin aluni versal connection with the said spin is, said support and carrier head holding the spindle at all times in a position at one side of theaxis of rotation of said work holder, said support being hinged to permit it and it carrier head and spindle to be raised and lowered out of and into ,operative positioh with respect to the work. holder.

10. In a grinding apparatus for producing spherical surfaces, the combination with a horizontal rotatable work holder, of a vertically disposed driving spindle, a carrier head provided with bearings for said spindle, a support'for said earner head connected thereto by a horizontally disposed .pivot, and an annular grindin tool having a universal connection with t c said spindle, said support and carrier head holding the spindle at all times in a position at one side of the axis of rotation of said work holder, said support being hinged to permit it and the carrier head and spindle to be raised and lowered out of and into operative, position with respect to the work holder and an adjustable stop for limiting the movement of' said support and its connected parts in a direction toward the work holder, to determine the position of the spindle and tool with respect to the work holder.

' 11. In an apparatus for grinding spherical surfaces, the combination with a plurality of rotatable grinding tools each provided with a grinding surface located at a dis-' tance from its axis of rotation, a work holder, said tools being located with res ect to the work holder, on opposite sides 0 the thework holder and the axes of said tools,

means forholding the said tools between the axis of said relative rotation, and the periphery of the work, and at different distances from the said axis 'of rotation;

12; In an apparatus for grinding spherical surfaces, the combination with a plurality of rotary annular grinding tools, a rotatable work holder, means for holding said tools laterally of the axis of rotation of said work holder, and on opposite sidesof the line of demarcation bet-ween the surfaces to be ground, means for driving said tools, and means for rotating said'work holder.

13. In an apparatus for grinding spherical surfaces, the combination with a plurality of grinding spindles, a grinding tool for each spindle, connected therewith by a universal joint-,jand provided with means for securing its rotation with its connected spindle, a work holder, means for causing a relative circular movement between said work holder and the axesof said tools, and means for'holding the said tools between the axis of said relative rotation, and the pe- "riphery of the work, and on opposite sides of the line of demarcation between the surv faces to be ground. v

14. In an apparatus for grinding spherifbal surfaces, the combination with a rota table grinding tool havin its grinding surface located at a distance Irom its axis of ro tation, whereby said tool abrades in an annular path, a work holder, means for rotatcireular movement of the tool and the work '100 ing said tool, means for causing a relative I holder; means for supporting said tool so a that it is free to move angularly with respect to its axis of rotation in all directions and means .for holding said tool at a distance from the axis of relative rotation.between the tool and the work holder.

15. In an apparatus for grinding spherical surfaces, the combination with a grinding tool having an annular grinding surface located at a distance from its axis of rotation and being capable of abrading in an annular path, a rotatable work holder having its supporting surface adjacent to the said annular grinding surface, means for-supporting said tool at one side of the axis of thework holder, a driving spindle for'said tool, a universal connection between the tool and said spindle and means for driving said'spindle.

MALCOLM BENTZON. 4 ALFRED HEJRY' EMERSON. Witnesses:

C. REDrnnN, 

